In rubber compositions adhering with a wire used for belt parts of a pneumatic tire, particularly a brass-plated wire, attempts have been made to mix DZ (i.e., N,N-dicyclohexyl-2-benzothiazolylsulfenamide), which is an accelerator having a slow vulcanization speed, and a large amount of sulfur to improve the adhesion property with the wire (e.g., see Ishikawa, Yasuhiro: Journal of the Japan Rubber Society, 65, 86 (1992)). Furthermore, as a vulcanization agent capable of supplementing the heat aging resistance of the rubber vulcanizate adhered with the brass-plated wire, an organic cyclic sulfide may be mentioned, but the adhesion property thereof was not satisfactory.